Weighing arrangement

ABSTRACT

A weighing arrangement includes an infeed for product material to be weighed and at least one dosing mechanism for controlled conveying of product material portions from the infeed to a weighing system. The dosing mechanism includes a motor-driven transport screw formed as a helically-shaped rod positioned in an open trough for conveying the product material from the infeed to the weighing system, and a control unit for controlling the motor in order to deliver a desired portion of product material to the weighing system. This weighing arrangement provides a gentle, well-defined conveyance of product materials that are not suited for vibrational conveyance or conveyance by a screw conveyor in a tubular housing.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit, under 35 U.S.C. §119(e), of co-pending provisional U.S. Application No. 60/677,524, filed May 4, 2005, the disclosure of which is incorporated herein by reference.

FEDERALLY-SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a weighing arrangement such as a multihead weigher comprising an infeed or storage hopper (both to be named as infeed) for product material to be weighed, and at least one dosing mechanism for controlled conveying of product material portions from said infeed to a weighing system.

2. Background Art

In weighing arrangements of this kind, it is known to use a dosing or batching mechanism comprising vibratory pans positioned as a trough for conveying product material from the infeed to the weighing system and to control the vibration in time and intensity in order to deliver a desired portion of product material to the weighing system. Such weighing arrangement can be used for a broad range of product materials, as long as the product materials can be conveyed by vibration in a sufficiently stable and organized manner. An alternative way of providing the delivery of desired portions of product material to a weighing system is to provide a screw conveyor in a tubular housing, which is suitable for controlled transport of particulate or pulverulent materials, such as e.g. known from EP 1 439 379. However, normal screw conveyors impose a relatively high mechanical influence on the product material. Such mechanical influence should, however, be avoided in connection with sensitive products. Thus, in connection with sensitive, sticky and/or flexible product materials, such as poultry, fish, fresh meat, marinated meat and corresponding lumpy and/or sticky materials, neither the vibrational nor the screw conveyor conveyance of the product material will be sufficiently stable, well-defined, and gentle, and will, thus, not be providing the required conveyance of these types of products.

SUMMARY OF THE INVENTION

It is the object of the present invention to provide a weighing arrangement of the kind referred to above, with which it is possible to provide a well-defined conveyance of product materials, which are not suited for vibrational conveyance. This object is achieved with a weighing arrangement for weighing sticky and/or flexible product material, such as fresh meat, marinated meat, poultry, fish and corresponding lumpy and/or sticky materials, which according to the present invention comprises:

-   -   an infeed for product material to be weighed; and     -   at least one dosing mechanism for controlled conveying of         product material portions from the infeed to a weighing system;     -   wherein the dosing mechanism comprises a motor-driven transport         screw formed as a helically-shaped member positioned in an open         trough for conveying the product material from the infeed to the         weighing system, and a control unit for controlling the motor in         order to deliver a desired portion of product material to the         weighing system.

The above arrangement comprises motor-driven transport screws formed as a helically-shaped member and providing a well-defined conveyance of product material from the infeed to the weighing system, even if the product material is sticky and/or flexible, or for other reasons is not suited for vibrational conveyance.

The positioning of the screw in an open trough provides a gentle conveyance, without imposing any significant mechanical influence or pressure on the product material.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following detailed part of the present description, the invention will be explained in more detail with reference to the exemplary embodiment of a weighing system according to the invention shown in the drawings, in which:

FIG. 1 shows a top view of the infeed for product material and eighteen motor-driven transport screws positioned in troughs for conveying the product material from the infeed to a weighing system;

FIG. 2 shows a cross sectional view of the arrangement in FIG. 1, taken along line along line A-A of FIG. 1; and

FIG. 3 shows a detail, enclosed within the circle B in FIG. 2, indicating an example of a connection between the motor and the transport screw.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus shown in FIG. 1 comprises an infeed 1 having eighteen dosing mechanisms 3 positioned symmetrically along the circumference of the infeed 1. Eighteen is considered an exemplary number of dosing mechanisms, but the number in practice may be as few as two, and as many as forty or more. Each dosing mechanism 3 comprises a trough 4, in which a transport screw 5 in the form of a helically-shaped member is positioned and driven by a motor 7 (see FIG. 3). The trough 4 comprises a bottom part with a diameter that is greater than or equal to the outer diameter of the transport screw 5. Positioned coaxially with the transport screw 5 is a core 6, which is considered to be optional, and which core 6 may have any diameter less than or equal to the inner diameter of the transport screw 5.

The infeed 1, shown in cross section in FIG. 2, comprises a conical central part 2, which provides a distribution of product material towards a peripheral outer wall 12 of the infeed 1. The conical central part 2 of the infeed ends at a distance from the outer wall 12 of the infeed, and therebetween the product material falls down into the individual troughs 4, in which the transport screw 5 and the optional core 6 are positioned to convey product material radially out of the infeed 1 in a controlled manner in order to deliver controlled portions of product material to a weighing system 15 positioned below the radially outer end of the troughs 4.

Preferably, the helically-shaped member of the transport screw 5 has an increasing pitch along its length in order to improve the gentle transport of the product material. As shown in FIG. 3, the connection between the motor 7 and the transport screw 5 comprises a bushing 8 onto which the transport screw 5 is connected permanently, e.g. by welding. Alternatively, the bushing 8 may be integrated into the core 6, if the latter is present. The bushing 8 comprises a pin 9 providing a non-rotational connection to a motor-driven axle 14 and a click-connection mechanism 10, e.g. provided by means of a spring (not shown) and a ball (not shown), the ball being pressed into a recess provided in the motor axle 14. The click-connection mechanism 10 allows for ease of assembly and disassembly for cleaning, maintenance, and replacement of the transport screw 5 and/or the core 6.

The motor 7 is preferably positioned in an inner motor compartment defined within the confines of the outer wall 12 and under the conical central part 2. The troughs 4 extend through corresponding openings in the outer wall 12 of the infeed 1. In order to avoid leakage of product material from the troughs 4 into the inner motor compartment, a sealing arrangement 11 is provided between the motor axle 14 and the outer wall 12 of the trough 4.

The mounting of the motor 7, and the possible provision of supplementary bearings (not shown) for the axle 14 of the motor, are provided in a conventional way, and no detailed explanation is required at this point for those of ordinary skill in the art.

The components in contact with the product material are preferably made of stainless steel, but other materials, such as plastic, for example, can be used for different reasons.

The above-described apparatus functions in the following way: Product material to be weighed is conveyed to the infeed 1 in a controlled manner in order to keep a mainly constant level of product material in the infeed 1. The product material is distributed to the individual dosing mechanisms 3 by the conical central part 2 of the infeed. Suitable sloping surfaces between the individual troughs 4 of the dosing mechanisms 3 may be provided in order to lead the product material into the individual troughs 4. Each dosing mechanism 3 delivers predetermined portions of product material to the related weighing system 15 by signals from a control unit 17 for the overall control for the weighing arrangement. The control unit 17 is operable to control the rotational speed and/or operational duration of the motor 7 so that a controlled, well-defined portion of product material is delivered by the controlled speed of the motor 7 during a controlled period of time. In order to optimize the dosing, the subsequent weighing of the delivered portion by the weighing system provides a signal that is fed to the control unit 17, which is then operated to adjust the period of time and/or the motor speed in order to adjust the dosage of product material from each individual dosing mechanism 3.

Typical values for the rotational speed of the transport screw 5 are 10-100 revolutions per minute, and typical periods of running times are between 50 and 2000 ms.

The following weighing and combination of dosed partial portions to final portions shall be as close as possible to the desired weight of the final portions by combining a predetermined number of dosed and weighed portions, is well-known within the art, and need not be explained in further detail.

The invention has been described above and explained in connection with a specific embodiment thereof, as shown in the drawings; however, many variations are evident for those skilled in the art without departing from the following claims. Among such natural deviations are variations in the number of dosing mechanisms 3, the provision of cores 6 having a smaller diameter, the provision of removable or replaceable cores and/or transport screws having different diameters for conveying different products and/or providing different speeds of conveyance, and the possibility of providing the core 6 with another outer form other than the cylindrical form shown in the drawings, such as, for example, a fluted form. Furthermore, the core may be kept stationary while rotating the transport screw 5 instead of being rotated synchronously with the transport screw 5. It will also be evident that the opening in the side 12 of the infeed 1, through which the trough 4 extends, has to be adapted to the product material to be conveyed by the dosing mechanism 3. 

1. A weighing arrangement for weighing sticky and/or flexible product material, such as fresh meat, marinated meat, poultry, fish and corresponding lumpy and/or sticky materials, comprising: an infeed for product material to be weighed; and at least one dosing mechanism for controlled conveying of product material portions from said infeed to a weighing system; wherein the dosing mechanism comprises: a transport screw positioned in a trough for conveying the product material from the infeed to the weighing system; a motor driving the transport screw; and a control unit that is operable to control the motor to deliver a desired portion of product material to the weighing system.
 2. A weighing arrangement in accordance with claim 1, wherein the transport screw comprises a helically-shaped member with an increasing pitch along its length.
 3. A weighing arrangement in accordance with either of claims 1 or 2, wherein the transport screw has an inner diameter, the arrangement further comprising a core positioned inside the transport screw, the core having a diameter that is less than or equal to the inner diameter of the transport screw.
 4. A weighing arrangement in accordance with claim 3, wherein the core has a substantially cylindrical form.
 5. A weighing arrangement in accordance with claim 3, wherein the core is rotated synchronously with the transport screw.
 6. A weighing arrangement in accordance with claim 3, wherein the core is kept stationary.
 7. A weighing arrangement in accordance with claim 3, wherein the core has a fluted outer surface.
 8. A weighing arrangement in accordance with claim 3, wherein the core is replaceable with a core of a different diameter for conveying a different product and/or providing different speeds of conveyance.
 9. A weighing arrangement in accordance with either of claims 1 or 2, wherein the trough comprises a bottom part having a diameter equal to or larger than the outer diameter of the transport screw.
 10. A weighing arrangement in accordance with claim 9, wherein the infeed includes an outer wall, and wherein the trough extends through an opening in the outer wall.
 11. A weighing arrangement in accordance with either of claims 1 or 2, wherein the infeed comprises a conical central part leading the product material radially outwards to several dosing mechanisms positioned in a circular pattern around the conical central part.
 12. A weighing arrangement in accordance with claim 11, wherein the motor is positioned under the conical central part of the infeed.
 13. A weighing arrangement in accordance with claim 3, wherein the motor has an axle, and wherein the transport screw and the core are connected to the motor by a click-connection mechanism for easy assembly, disassembly, cleaning and replacement of the transport screw and/or core.
 14. A weighing arrangement in accordance with either of claims 1 or 2, wherein the motor is controlled in speed and running time by the control unit.
 15. A weighing arrangement in accordance with claim 14, wherein the control unit receives information from the weighing system on the weight of the material portions and is operable to adjust the speed and/or running time in dependence thereof.
 16. A weighing arrangement in accordance with either of claims 1 or 2, wherein the arrangement comprises 2-40 dosing mechanisms. 